This invention relates generally to magnetic head transducers and more particularly to a laminated, high frequency, magnetic transducer for a head for use with a magnetic tape media, plus a method for producing such a transducer.
The performance of a magnetic tape recorder depends heavily on the properties of the magnetic materials used to make the recording heads and tapes and on the structural configuration of these materials which influence their magnetic properties. Magnetically hard materials, characterized by their high remanence, high coercivity, and low permeability, are chiefly used in the manufacturing of the recording tape and other related recording media. On the other hand, magnetically soft materials, which exhibit low coercivity, low remanence, and relatively high permeability, are commonly utilized to make the magnetic cores for the heads which are the means by which electrical signals are recorded on and reproduced from the magnetic tape.
For a video recorder, the typical ring-type magnetic video head is composed of two highly permeable magnetic cores, with a nonmagnetic gap spacer and a coil to which signal information is connected. The record video head is a transducer that changes the electrical energy from the signal system into a magnetic field that is emitted from a physical gap in the video head which impresses a magnetic pattern on the magnetic tape proportional to the electrical signal. The reproduce video head, conversely, is a transducer that collects the flux from the magnetic tape across a physical gap and changes it into an electrical signal that is proportional to the recorded flux.
Ferrite materials have been conventionally used as the magnetic material in video heads. The advent of high-definition video tape recorders, digital video tape recorders, and the like, with the resultant use of high coercivity recording media such as metal powder media, metal evaporated media etc., have accelerated the trend towards high density construction for recording even larger amounts of information. As part of this evolution, there is the resultant need to increase the frequency of the information signal recorded on the medium. Conventional ferrite cores are simply incapable of providing the desired characteristics to achieve the required performance for these applications. Due to its inherent brittleness, ferrite cores cannot be made into narrow track widths or thin magnetic core laminations since the consequent chipping and breaking of the ferrite material during the fabrication process cannot be eliminated.
In addition to the fabrication problems associated with ferrite heads, there are performance problems, particularly when such heads are used with high coercivity magnetic tape, and particularly during the recording process. During recording, larger signals are required with high coercivity magnetic tapes than with conventional magnetic tapes. The problem is not severe with the use of ferrite heads during reproduce operations, since signal levels from the tape are much lower in magnitude. With higher recording signals and smaller heads, the signal tends to drive the ferrite heads into saturation. On reproduce or "playback", it has also been observed that there is a significant noise level resulting from contact of such high coercivity magnetic tapes with the ferrite heads, which, in turn, requires more signal to achieve an acceptable signal to noise ratio. Bulk metal heads likewise have performance disadvantages, one of the more significant disadvantages being that they have poor high frequency response, principally because of eddy current losses.
The above considerations have led to the use in recording heads of any number of other commercially available magnetic materials which have higher flux density saturation, such materials including cobalt-zirconium-niobium (CZN) alloys, iron-aluminum-silicon alloys including Alfesil, Sendust, Spinalloy, or Vacodur each having a nominal composition of 85% iron, 6% aluminum, and 9% silicon, and also amorphous metals.
Besides the magnetic properties of the head core materials used, the critical design considerations that dictate performance of the video heads are track width, gap length, gap depth, core cross-sectional area, and other core geometry (e.g. path length). Each of these parameters must be selected in accordance with the design criteria of the magnetic tape recorder, while, at the same time, maintaining the head efficiency as high as possible.
There exists, therefore, a significant need for an improved high frequency magnetic transducer having a short magnetic path to reduce core reluctance and make the reduced core reluctance less dependent on the permeability of the magnetic material used in the magnetic cores. In addition, eddy current losses and other frequency effects should be minimized. Pole tip wear should also be minimized and leakage reluctance reduced. Ideally, such heads should provide good high frequency response and have characteristics such that the saturation of the core material does not occur at normal recording levels. The fabrication of such a transducer should be high volume, high accuracy, low cost and achieve a high degree of uniformity. The present invention fulfills these needs and provides further related advantages.